Information technology (“IT”) managers face a number of challenges as they are increasingly pushed to improve service delivery while lowering operational costs. These challenges include decreasing “server sprawl”, improving system utilization, reducing system management complexity, and improving the flexibility of IT resources. To address these challenges, many IT organizations are implementing some form of server consolidation using bladed servers.
Bladed systems are those in which individual servers are implemented as removable rack-mounted blades. In general, a bladed system includes some combination of the following features: hot insertion and removal of blades, consolidation of cables, integrated system management software, and automated software deployment. Currently available blades may include one to four central processing units (“CPUs”) and a typical bladed server may hold in the range of 48 to 250 CPUs.
A processing area network (“PAN”) architecture, as exemplified by the bladed systems available from Egenera, Inc., is one approach used to design and implement bladed servers. A PAN architecture includes the components required to implement multiple servers on a single bladed system, i.e., the hardware, software, and network and I/O resources. Specifically, a PAN architecture may include processing resources, integrated networking, centrally managed network and storage resources, management software, and operating system software. This architecture provides for high availability clustering with such features as load balancing and automatic hardware failover.
Bladed systems comprising a PAN architecture also include functionality supporting automatic failover of software or applications. Application failover in this context requires a redundant, passive failover blade and the installation of the application software, operating system, and all required support software on at least two disks—one active and one passive. The dedicated, i.e., passive, boot disk is required to have the same configuration as the primary, i.e., active, boot disk. That is, the failover boot disk must have the identical version of the application installed along with the same operating system, support software, etc. In addition, a third disk is required to store any application data that persists between executions of the application. This failover implementation also requires three internet protocol (“IP”) addresses, one for the primary blade, one for the failover blade, and a floating IP address that moves with the application. The PAN management software monitors the application as it executes on the active blade. If that application fails, the PAN management software activates the application on the passive blade using the passive disk.
While this approach to application failover provides for high availability of critical applications, it increases overall system cost and contributes to under-utilization of system resources. Multiple licenses for the application and any required support software must be purchased. Additional maintenance time is required as each time a new patch release, service pack, upgrade, etc. is installed on the primary boot disk, it must also be installed on the failover boot disk. In addition, a redundant, passive blade server and a disk must be dedicated to each application configured for automatic failover and multiple IP resource addresses must be administered.